Apparatus for rapidly forming deep draws in metal sheets



ORS H21.

M. WATTER EIAL APPARATUS FOR RAPIDLY FORMING DEEP DRAWS IN METAL SHEETSFiled Dec. 20. 1955 INVENT MLChCL-Ql Wcl (Ta reR D. Pag 4 ATTORNEY i0 i,FIG.2

Aug. 19, 1958 United States Patent APPARATUS FOR RAPIDLY FORMING DEEPDRAWS 1N METAL SHEETS Michael Watter, Philadelphia, and Garrett D.Pagon,

Ambler, Pa., assignors to The Budd Company, Philadelphia, Pa., acorporation of Pennsylvania Application December 20, 1955, Serial No.554,165

3 Claims. (Cl. 1 l3-44) This invention relates to apparatus for rapidlyforming deep draws in metal sheets and has for an object the provisionof improvements in this art.

The method commonly used to produce deep draws in sheets includes thesteps of rigidly gripping the edges of the sheet by jaws and strikingthe sheet by mechanically operated dies. The impact tends to rupture themetal so that only a small amount of work can be done at one operation.This requires many operations for deep draws, is very expensive, andusually requires heat treatment between operations. The expense isgreatly increased because a different die set must be used for eachoperation. Besides, the metal tends to buckle near the gripped edges andwhen these buckles or wrinkles are started they are hard to remove.Further than this, considerable metal is lost in the gripped edges whichmust be cut off.

According to the present invention very deep draws can be made at asingle operation. There are no sudden blows and the likelihood of metalrupture is greatly minimized or eliminated.

The method comprises the guiding of a sheet at its edges around itscircumference and applying fluid pressure radially inwardly to the edgesof the sheet completely around its periphery. The edges are disposedbetween circumferential confining and sealing members which preventescape of fluid inward but which permit the edges to move inward underpressure as the intermediate part bulges axially. The metal tends toflow axially interiorly of the space where the edges are guided becausethere is less opposite to flow in this direction than elsewhere, withincertain limits. As an aid to axial movement, an axial pressure isapplied. The radial pressure acts upon a much smaller exposed surfacethan the normal or axial pressure and is usually many times as great perunit area as the normal pressure. sure'forces could be applied bymechanical means, but for simplicity and controlled application it ispreferable to use fluid pressure.

The detailed objects of the invention are: To make deep draws withoutrupture; to use as much of the original sheet stock as possible; toreduce the number of operations to attain a given depth of draw;toreduce the die cost to a minimum; and in other ways to provide animproved method and apparatus for making deep drawn sheets.

The above and other objects and certain advantages of the invention willbe apparent from the following description of an illustrativeembodiment, reference being made to the accompanying drawings, wherein:

Fig. l is a central axial section, partly diagrammatic in nature,showing the die apparatus used in the invention; and

Figs. 2, 3, 4 and 5 are perspective views of a conical article atdifferent stages of formation according to the present invention.

As shown in Fig. 1, a blank or workpiece W, which is to be formed into acone, is placed in mating dies and The axial pres- 2,847,957 PatentedAug. 19, 1958 11 which closely confine the edges of the blank in anannular zone around the circumference to keep it from buckling. Sealingmeans, such as rubber O-rings 13 in V-shaped grooves located at a radialdistance within the outer periphery of the annular zone, insure thesealing of the edge around its circumference for the full range ofaction on the blank, that is for the full inward movement of its outerperiphery. The die surfaces are preferably ground smooth for easyslippage of the blank edge between them.

One die part, such as 10 here, is formed with a cavity 14 into which themetal may expand and to give it form; and the other die part 11 isformed with means to receive the pressure fluid, as from a channel 16and pipe 17.

Outside the sealing rings 13, at the radial distance left for blankcontraction and at the outer periphery of the die 10, or die 11,whichever moves axially, or both, the die parts are formed with acircumferential cavity 18 to receive pressure fluid, as from a channel19 and a pipe 20.

The die parts 10, 11 shown herein are formed as separate parts,selective as to shape, which are secured in a case 22, as by a screwretainer 23, sealing rings 24 being used on each side of the channel 18.

The pressure fluid may be provided in various ways, as by an explosiveor by pumps with accumulators and sudden release means, by pumps alone,or the like. As stated, the radial pressure is greater per unit areathan the axial or normal pressure, say about ten times as great. Forexample, for sheet material of /s" thickness an axial pressure of 5,000lbs/sq. in. and a radial pressure of 50,000 lbs/sq. in. has been usedsuccessfully. The disk diameter at the start was about 7 /2".

The dies may be held together by any suitable means, such, for example,as the threaded assembly illustrated, by bolts, by placing in a press,or the like.

Figs. 2, 3, 4 and 5 show successive stages in the formation of thearticle. Preferably, though not necessarily, the blank W, Fig. 2, ispreliminarily formed with a starting bulge, as W1. This may be formed ona mechanical press. It seems to aid in initiating the metal movement tosome extent. The shapes shown in Figs. 3, 4 and 5 may represent variousforms made on successive die sets or may represent transition stages ina single die set.

As an illustrative example, a blank of 7 /2" diameter and A5 thicknesswas drawn into a cone 3" deep. The final diameter over the flange wasabout 5". The flange gradually narrowed as the conical protuberance wasformed and increased in thickness somewhat as the conical pa rt becamethinner.

If a source of fluid of sutficiently high pressure is steadilyavailable, the full draw may be made in one step, but if the pressuredrops after application, it may be necessary to work in several stages.With steady expansion without sudden impact, the metal will flowproperly without tearing whether the full action is affected in one stepor several.

The dies illustrated have a curved throat which aids in directing themetal flow, but it has been found that the metal will flow axially fromthe radial edges even when a curved throat is not provided. Neither isit necessary to give the blank an initial cupped shape.

it has been found that articles drawn according to the present methodand with the present apparatus have no abrupt thinning or incipienttearing and use a greater proportion of the blank stock than other knownmethods.

It is thus seen that the invention provides an improved process andapparatus and provides an improved product.

While one embodiment of the invention has been disclosed for purposes ofillustration, it is to be understood that there may be variousembodiments within the general scope of the invention.

What is claimed is:

1. Apparatus for forming deep-drawn sheet metal parts from generallyflat sheet metal blanks, comprising in combination, mating axiallyconvergent dies formed and arranged to clamp a blank in an annular outerzone, leaving the inner zone unclamped with space to expand axially,means in said dies forming an annular fluid chamber outside said annularzone, means to admit fluid under pressure to said annular fluid chamberto apply uniform pressure radially inwardly on the blank around itsentire outer periphery, means sealing the space outside said annularchamber against the leakage of fluid therefrom, means at a distanceradially within the outer periphery of the annular zone providing a sealagainst inward leakage of fluid between the blank and dies, and meansfor separately and independently applying axial pressure on the blank inthe inner unclamped zone while fluid pressure is being applied to theouter periphery of the blank in the clamped zone to form an axialprojection in the inner unclamped zone.

2. Apparatus as set forth in claim 1, wherein one of said dies fits inthe bore of a surrounding case member with its outer periphery formingthe outer border of said annular clamping zone at said annular fluidchamber, and in which outer fluid sealing means are provided betweensaid case member and the die therein.

3. Apparatus as set forth in claim 1, wherein said means for separatelyand independently applying axial pressure comprises fluid pressure meanswhich is controlled separately and independently of the radially actingfluid pressure means.

References Cited in the file of this patent UNITED STATES PATENTS1,530,000 Kauflman Mar. 17, 1925 2,203,868 Gray et al June 11, 19402,331,430 Shoemaker Oct. 12, 1943 2,615,411 Clevenger et al. Oct. 28,1952 20 2,649,067 Kranenberg Aug. 18, 1953

